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ZigZagZ: Improving mechanical performance in extrusion additive manufacturing by nonplanar toolpaths

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journal contribution
posted on 29.01.2021, 14:01 authored by James Allum, Jeremy Kitzinger, Yimeng Li, Vadim SilberschmidtVadim Silberschmidt, Andy GleadallAndy Gleadall
© 2020 Elsevier B.V. This study investigates the effect of novel non-planar deposition methods in fused filament fabrication (FFF) additive manufacturing. A range of non-planar geometries were developed including a ZigZagZ sequence in which filaments were deposited as the nozzle moved in the X or Y direction while simultaneously zigzagging up-and-down i.e. in the Z direction. As a result, repeating non-planar layers were generated throughout the specimen's geometry. The use of the ZigZagZ toolpath to deposit the material significantly improved the mechanical performance of parts manufactured by FFF in the Z-direction by up to 62% in strength, 123% in strain-at-fracture and 245% in toughness compared to an optimised conventional planar geometry. All specimens in the study had only a single filament through their thickness; they were specially developed to enable precise mechanical characterisation. This is the first work to have developed and analysed nonplanar deposition with cyclic nonplanar nozzle movement of a geometric length scale similar to the nozzle diameter. Three novel toolpath designs were developed for this study: (i) zigzag (ZZ), based on the aforementioned ZigZagZ deposition; (ii) up-down (UD) involving vertically deposited nonplanar bulges with interconnecting planar sections; (iii) forward-back (FB) employing the nozzle's movement forward and backward during planar deposition to enhance the nozzle's contact and promote the ploughing of the deposited filament. These designs - along with the conventional planar toolpath designs (original (OR)) - were characterised and their mechanical properties compared to generate new understanding about the impact of deposition with the Z coordinate varying along the path on performance. The geometrical outcomes of these different deposition strategies were analysed microscopically to assess the effects of nonplanar toolpaths on the filament-scale geometry. It was established that the ZZ strategies resulted in higher extruded-filament thickness compared to OR. Additionally, various ZZ designs were developed to understand the impact of the zigzag height-to-width ratio and size not only on mechanical properties, but also geometry and fracture path. Fractographic analysis indicated that nonplanar FFF extrusion promoted through-filament fracture, suggesting a reduced concentration of stresses at interlayer bonds by redirecting the load into the filament; this could contribute to the increased level of toughness observed in ZZ specimens. The understanding developed in this study is readily adaptable for the use in both single-wall and infill geometries to provide their improved mechanical performance. A broad range of potential industrial applications and research relevance resulting from the findings is discussed in addition to future development opportunities.

History

School

  • Mechanical, Electrical and Manufacturing Engineering

Published in

Additive Manufacturing

Volume

38

Publisher

Elsevier BV

Version

AM (Accepted Manuscript)

Publisher statement

This paper was accepted for publication in the journal Additive Manufacturing and the definitive published version is available at https://doi.org/10.1016/j.addma.2020.101715

Acceptance date

12/12/2020

Publication date

2020-12-14

Copyright date

2021

ISSN

2214-8604

eISSN

2214-8604

Language

en

Depositor

Mr Andy Gleadall Deposit date: 25 January 2021

Article number

101715